JP3276642B2 - Transactional synchronous access to sequential files - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronously accessing a sequential file using a non-volatile memory.

[0002] When data generated in the processing of an online transaction is stored in a sequential file,
There is a need for a technology that improves processing performance and space efficiency in a storage medium.

[0003]

2. Description of the Related Art FIG. 5 shows an example of the prior art. In FIG. 5, reference numeral 10 denotes a space in which an application program runs (hereinafter, referred to as an application space); 13, an exclusion mechanism for performing exclusive control of file access; 16, a page buffer; 17, an order in which records are sequentially stored. Represents a file.

In the prior art, when a record write request is issued after the start of a transaction, the record is stored in a page buffer 16 composed of a volatile memory, and when the transaction ends, the exclusive mechanism 13 sends the record to the sequential file 17. Exclusive access right (hereinafter, referred to as exclusive), and the transaction target record existing on the page buffer 16 has been written to the sequential file 17. Thereafter, the exclusion of the sequential file 17 was released.

[0005]

FIG. 6 is a diagram for explaining the problems of the prior art. When transactions occur consecutively in the sequential file 17, input / output (I / O) to the file medium is output at the end of each transaction, so there is a performance problem that generally causes an I / O bottleneck. .

For example, when a record is reflected in the sequential file 17, if a record is to be added to the page where the last record exists, the page is temporarily transferred from the sequential file 17 as shown in FIG. It is necessary to perform a process of reading, adding a record to the read page, and reflecting the page in the sequential file 17. However, if this processing is performed, at least two I / Os are required to store the record, and there is a performance problem.

As shown in FIG. 6B, a method of adding a record to the page next to the page where the last record exists is conceivable and used so that this can be done by one I / O. I have. However, in the case of this method, if the records are not fully contained in each page, the file efficiency is deteriorated. For example, if one page is 4096 bytes and the size of a record to be stored is 512 bytes, the space of (4096-512) bytes per page becomes an empty area, and becomes a useless area that is not used thereafter.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to realize transaction synchronous access to a sequential file which can improve performance at the end of a transaction and improve space efficiency of a file.

[0009]

FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. 1, reference numeral 10 denotes an application space in which an application program runs, 11 denotes a transaction control unit that controls the start and end of a transaction, 12 denotes a file system that provides a file access function, and 13 denotes exclusive control of file access. , A record buffer composed of a volatile memory, 15 a nonvolatile memory for storing records, 16 a page buffer, and 17 a sequential file in which records are sequentially stored.

The present invention is realized, for example, by a computer system having a generally known hardware configuration for online data processing. In the present invention, a record storage nonvolatile memory 15 for temporarily storing records written out in a transaction is provided. Then, at the end of each transaction, instead of reflecting the completed record in the sequential file 17, the record is stored in the record storage nonvolatile memory 15.

The records stored in the record storage nonvolatile memory 15 are ultimately reflected in the sequential file 17, but the trigger is that the record storage amount in the record storage nonvolatile memory 15 is limited. This is when the amount has exceeded a predetermined amount. For example, the nonvolatile memory 1 for storing records
When 5 is full, that is, when no more records can be stored, it is reflected on the sequential file 17 via the page buffer 16. Only when a page is written from the page buffer 16 to the sequential file 17, the exclusion mechanism 13 needs to acquire the exclusion of the sequential file 17.

When a system or an application program executing a transaction crashes while a record is present in the record storage nonvolatile memory 15, the record storage nonvolatile memory 15
Since the above record is not lost, by reflecting it in the sequential file 17 at the time of the recovery processing, it is possible to guarantee the record for which the transaction has been completed.

A file is composed of a plurality of (one or more) pages, and each page is composed of a plurality of (one or more) records. A record is a unit of data recognized by an application program.

[0014]

If there is an empty area in the record storage nonvolatile memory 15, the I / O is performed at the end of each transaction.
Does not appear, but the nonvolatile memory 1 for storing records
The transaction end process is completed only with access to No. 5.

Since the process at this time is only access to the record storage nonvolatile memory 15, there is no need to obtain exclusion for the file unlike the conventional method. This is because, by acquiring the record storage nonvolatile memory 15 corresponding to a transaction, it is possible to prevent contention for access with another transaction.

Since the I / O is issued to the sequential file 17 only in principle when the record storage nonvolatile memory 15 becomes full, a plurality of transactions occur consecutively. In this case, the performance of the entire processing is improved as compared with the conventional method.

For example, when the amount of the non-volatile memory is set to 4096 bytes and a process of writing one 550-byte record in one transaction is considered, the record storage is performed at the time of seven record processing, that is, at the time of seven transaction processing. The non-volatile memory 15 becomes full, and is reflected in the sequential file 17 in the next transaction processing. As a result, I / O is output only once in seven times, and the performance is remarkably improved as compared with the related art in which I / O is output every time.

Further, for example, by matching the size of the record storage nonvolatile memory 15 with the size of a page (unit for storing a plurality of records) constituting the sequential file 17, the record storage nonvolatile memory 15 can be used. Memory 1
If the record is reflected on the page in the sequential file 17 in the state where the number 5 is full, the page on the file medium is
The record is full. by this,
It is also possible to improve the space efficiency on the medium.

[0019]

FIG. 2 shows an embodiment of the present invention when there is no file reflection by transaction synchronous access, and FIG. 3 shows an embodiment of the present invention when there is file reflection by transaction synchronous access.

(A) Transaction control unit 11 Transaction control unit (hereinafter referred to as LTC) 11
Is a mechanism that controls the start and end of a transaction. This makes adjustments to ensure consistency of all applicable files when a transaction is applied to multiple files.

The basic operation of the LTC 11 is as follows. At the end of the transaction, the LTC 11 issues a first end request to the file system 12. This is called a prepare request.

The success of this process depends on the file system 12
Then, the LTC 11 issues a second end request to the file system 12. This is c
Omit request. With this completion, the transaction end processing is completed.

In the case of transaction processing for a plurality of files, the LTC 11
Issue a repair request. All prepare
When the processing is completed, the next
t request is issued to complete the transaction end processing.

If at least one failure is notified for the prepare request, the LTC 11
issue a "repair invalid", which causes all prepar
e is invalidated and each file is returned to its original state. This ensures consistency of multiple files. In the following description of the embodiment, for simplification of the description, a case where there is one target file will be described as an example.

(B) Exclusion mechanism 13 This is a mechanism for serializing the target file in order to reflect the record in the file. Since multiple transactions may access the same file at the same time, it is necessary to serialize these requests.

When the record is reflected in the sequential file 17, the exclusion mechanism 13 first acquires the exclusion of the file, acquires the EOF (End Of File) information of the record, and updates it. Release the lock on the file when the reflection on the file ends.

(C) Record buffer 14 A buffer for storing records when writing records in synchronization with a transaction, and is composed of a volatile memory. Until the end of the transaction, the record requested to be written is stored in the record buffer 14.

The record buffer 14 is prepared for each file open. Storing records in the record storage non-volatile memory 15 via the record buffer 14 without directly storing the records in the record storage non-volatile memory 15 is because the access performance to the non-volatile memory is volatile. This is because the access performance to the record buffer 14 composed of the volatile memory is reduced. Records are stored in the record buffer 14, and the number of accesses to the record storage nonvolatile memory 15 is reduced as much as possible.

(D) Record Storage Non-Volatile Memory 15 This is a memory for storing records in the record buffer 14 at the end of a transaction, and is composed of a non-volatile memory, so that its contents are preserved even in the event of a system crash. This is also prepared for each file open.

The records stored in the record storage nonvolatile memory 15 are guaranteed to be reflected in the sequential file 17 after the end of the transaction. Actually, the records in the record storage nonvolatile memory 15 are reflected in the sequential file 17 when the record storage nonvolatile memory 15 becomes full or when the file is closed. In other words, even if the transaction ends, the record requested to be written is not always immediately reflected in the sequential file 17.

(E) EOF information managed by the exclusion mechanism 13 The EOF information is information indicating the storage position of the last record in the file. The EOF information is stored in a non-volatile memory and managed by the exclusion mechanism 13.

The file system 12 requests the exclusion mechanism 13 to acquire exclusive control of the non-volatile memory (EOF information) when reflecting the records in the record storage non-volatile memory 15 in the sequential file 17, thereby storing the EOF information. To win. Based on the acquired EOF information, the page buffer 16
Write the contents of to a file.

(F) Page buffer 16 This is an I / O buffer used to reflect records in the record storage nonvolatile memory 15 to the sequential file 17. The page buffer 16 is adapted to the file storage format.

The record storage nonvolatile memory 15 does not have a complete page structure like a page buffer used for ordinary record access, but has only a necessary minimum page structure. Therefore, the record storage nonvolatile memory 15 cannot be used as an I / O buffer. Therefore, the application space 10
A page buffer 16 is prepared.

The processing operation when the file is not reflected by the transaction synchronous access will be described below with reference to (1) to (5) shown in FIG. (1) When a file is opened, the nonvolatile memory 15 for storing records is allocated. When the file is opened, both the record buffer 14 and the record storage nonvolatile memory 15 are empty.

(2) The transaction is started, and in the record writing process, the record requested to be written is stored in the record buffer 14, and the record writing process is completed.

(3) When a transaction end declaration is made, L
Preparing from TC 11 to file system 12
An e request is issued. (4) Upon receiving the prepare request, the file system 12 moves the record in the record buffer 14 to the record storage nonvolatile memory 15, and
Complete the process. In this state, the prepare can be made valid or invalid.

(5) In accordance with a commit request from the LTC 11, the record moved to the record storage nonvolatile memory 15 is validated. Next, the processing operation when a file is reflected by transaction synchronous access will be described according to (1) to (10) shown in FIG.

(1) to (3) correspond to (1) to (3) shown in FIG.
Same as (3). (4) The file system 12 stores the pre-
When the pair request is accepted, the record in the record buffer 14 is to be stored in the record storage non-volatile memory 15, but is already in the full state. Therefore, it is determined that the records in the record storage nonvolatile memory 15 need to be reflected in the sequential file 17. Note that the record in the record storage nonvolatile memory 15 is already
It is a record for which it has been completed.

(5) In order to reflect the record in the sequential file 17, the file system 12 requests the exclusion mechanism 13 to obtain exclusion of the file, and requests to obtain the EOF information for knowing the writing position of the file.

(6) The file system 12 stores the record storage nonvolatile memory 1 in the page buffer 16 for I / O.
Move record 5 and build a page structure (a structure that can be reflected in the file).

(7) The records in the page buffer 16 are reflected in the sequential file 17 in page units based on the EOF information obtained in (5). (8) After storing the record in the sequential file 17, the EOF information is updated, and the acquired exclusion is released.

(9) Since the records in the record storage nonvolatile memory 15 are reflected in the sequential file 17, the records in the record storage nonvolatile memory 15 are cleared.
After that, the record in the record buffer 14 is stored in the record storage nonvolatile memory 15 and prepared.
Complete the process.

(10) In response to a commit request from the LTC 11, the record moved to the record storage nonvolatile memory 15 is validated. FIG. 4 is a flowchart when a record in the record buffer 14 is moved to the record storage nonvolatile memory 15 according to the embodiment of the present invention. The following processing procedures (a) to (h) are performed.

(A) The process of moving the record in the record buffer 14 to the record storage nonvolatile memory 15 is started. (b) At this time, if the record storage nonvolatile memory 15 is full, the process proceeds to (d). If not, (c)
Proceed to.

(C) The record in the record buffer 14 is moved to the record storage non-volatile memory 15 and the processing is terminated. (d) If the record storage nonvolatile memory 15 is full, the exclusion mechanism 13 acquires exclusion of the file,
Get EOF information.

(E) The record in the record storage nonvolatile memory 15 is moved to the I / O page buffer 16. (f) The pages in the page buffer 16 are reflected in the sequential file 17.

(G) Update the EOF information managed by the exclusion mechanism 13 and release the exclusion of the file. (h) The record storage nonvolatile memory 15 is cleared, and then the record in the record buffer 14 is moved to the record storage nonvolatile memory 15.

[0049]

As described above, according to the present invention,
By temporarily storing the transaction completed records in the non-volatile memory and reflecting them in the target sequential file collectively, the number of I / O times can be reduced and the performance can be improved. In addition, since the data can be reflected in the file in units of pages, useless space in the file can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention when there is no file reflection in transaction synchronous access.

FIG. 3 is a diagram showing an embodiment of the present invention when a file is reflected in transaction synchronous access.

FIG. 4 is a flowchart when a record in a record buffer is moved to a record storage nonvolatile memory according to the embodiment of the present invention.

FIG. 5 is a diagram showing an example of the related art.

FIG. 6 is an explanatory diagram of a problem in the related art.

[Explanation of symbols]

 Reference Signs List 10 application space 11 transaction control unit 12 file system 13 exclusion mechanism 14 record buffer 15 non-volatile memory for storing records 16 page buffer 17 sequential file

Continuation of the front page (56) References JP-A-2-138646 (JP, A) Masami Yamatani, Illustration of Computer Series File Organization, Japan, Ohmsha, July 30, 1985, P28-P30 (58 ) Field surveyed (Int. Cl. ⁷ , DB name) G06F 12/00 514 G06F 12/00 518

Claims (1)

(57) [Claims] A method for synchronously accessing a sequential file for storing records written by a transaction in a sequential file, comprising: a record storage nonvolatile memory for storing records written by a transaction; 15), and records the completed records of multiple transactions in the non-volatile memory for storing the records.
(15) is temporarily stored in the non-volatile memory for record storage (15) when the storage of the record in the non-volatile memory for record storage (15) reaches a predetermined amount or becomes full. A transaction synchronous access method to the sequential file, wherein the transaction is reflected in the sequential file (17) in a lump.